The Environmental Control of Individual Aqueous Particles in a Cubic Electrodynamic Levitation System

Abstract

ABSTRACT. The experimental investigation of aerosol particles often requires special apparatus to ensure that the walls of the system interfere minimally with the measurements. Electrodynamic levitation offers an attractive approach because the particle, when suitably charged, is held away from the system walls by time-dependent electric fields. A new electrodynamic levitation system has been developed expressly for investigating aqueous particles in controlled gaseous environments. A cubic cell was used in conjunction with the carefully controlled introduction of gas into the cell to form a wall-less flow reactor that is ideal for thermodynamic and kinetic studies involving reactive reagents. Unlike most previous cell configurations, the cubic geometry permits three-axis position control of the particle and an ability to measure the gravitational and drag forces simultaneously and independently when the gas flow is horizontally aligned. Preliminary results at room temperature of the mass gained by salt and sulfuric acid particles exposed to various humidities show the basic characteristics of the cell. New results with sulfuric acid particles exposed simultaneously to the vapors of water and nitric acid show that nonvolatile and volatile solutes cause aqueous particles to behave in qualitatively differentways. Such results confirm that cloud formation in the atmosphere should be enhanced by the presence of soluble trace gases under suitably low-temperature conditions.

Experimental Studies of Droplet Evaporation Kinetics: Validation of Models for Binary and Ternary Aqueous Solutions

“…Our ␣(HNO 3 ) values are slightly lower than those of Rudolf et al (2001), who put 0.3 as the lower limit based on binary condensation to small particles in an expansion chamber. But, the same arguments we have tentatively used to explain the empirical pressure dependence also lead us to expect ␣(HNO 3 ) to be relatively large over small particles at high supersaturations (Lamb et al 2004).…”

“…The principles of electrodynamic levitation have been described in the literature (see Hartung and Avedisian 1992; Allison and Kendall 1996;Davis 1997), and details of our specific system are available elsewhere (Lamb et al 1996), so only a summary is presented here. The principles of electrodynamic levitation have been described in the literature (see Hartung and Avedisian 1992; Allison and Kendall 1996;Davis 1997), and details of our specific system are available elsewhere (Lamb et al 1996), so only a summary is presented here.…”

“…A moderate DC voltage (ϳ150 V) was applied to a stainless steel cylinder surrounding the glass tip, while the top end of the injector was grounded, causing the liquid to become polarized (Lamb et al 1996). The body of the droplet injector was constructed of 1/8" outside diameter stainless steel tubing and contained a small reservoir for the working fluid near the top.…”

Phase Transitions of Aqueous Atmospheric Particles

“…[2][3][4][5][6][7][8] There is rapid development in the science of the phase transitions of atmospheric chemistry as well as a growing recognition of the importance of the condensed phase for diverse atmospheric problems. Laboratory work on cirrus and PSC cloud formation at low temperatures and salt crystallization at low relative humidities include 8 publications in 1999, 9-16 19 in 1997-1998, 17-35 14 in 1995-1996, [36][37][38][39][40][41][42][43][44][45][46][47][48][49] 18 in 1993-1994, 50-66 and 18 between 1977 and 1993. [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] Earlier work on salt crystallization is found in refs 85-88. In addition, there have been numerous papers describing field and modeling studies.…”

A History of Single Aerosol Particle Levitation

“…Thus, the drag force associated with a horizontal flow can be balanced with a dc field independently of the gravitational force using such a device. There is a renewed interest in the cubic device for studies in which flow through the chamber is needed (Lamb et al, 1996).…”